This invention relates to a sintered iron base friction material having a substantially constant wear rate up to 300.degree. C. and a substantially linear wear rate between 300.degree.-500.degree. C.
In recent years, disc brakes on automobiles have had to be able to operate under severe braking conditions in order to meet certain standards. During braking, such disc brakes have been subjected to operating temperatures that often exceed 300.degree. C. When organic brake linings operate at temperatures above 300.degree. C., as exponential wear rate is experienced and such linings have burst into flames resulting in a dangerous condition.
Even the most successful organic based friction linings of the type disclosed in U.S. Pat. No. 3,835,118, which use sponge iron as the principal friction modifier cannot operate above 300.degree. C. for an extended period of time without the resin matrix deteriorating.
It is known in the aerospace industry that sintered materials can be used as friction lining for aircraft brakes. As disclosed in U.S. Pat. No. 3,019,514, the matrix material is normally copper. Unforturnately for most automobile applications, the cost of copper renders such a friction lining too expensive for most customers.
U.S. Pat. No. 4,050,619 discloses substitution of iron powder for copper powder. However, since copper powder has a lower melting point and alloys with the fusible material at a lower temperature and/or impact pressure, iron powder has not been extensively investigated as the matrix material for production.